NEW YORK DAY BY DAY

By Susan Heller Anderson and Frank J. Prial

Published: March 17, 1984

through the Times Square subway station, then wheeled his double bass onto a No. 1 IRT train. Mr. Mensch is over 6 feet tall, about the same height as his instrument.

''Oh, I take it on the subway all the time,'' he said, ''It is a bit cumbersome.''

The bass fiddle, he said, is an Italian Gagliano, dated 1710. Mr. Mensch, who played in the New York Philharmonic from 1966 to 1975, teaches double bass at the Juilliard School, Mannes College of Music, Yale University and the Manhattan School of Music.

''Usually, people are very tolerant,'' he said, clutching the bass during a sudden lurch. ''But when it's crowded, sometimes they suggest I take up the flute.''